[PATCH] ns: introduce getnspid syscall

[PATCH] ns: introduce getnspid syscall

[Chen Hanxiao]

We need a direct method of getting the pid inside containers.
If some issues occurred inside container guest, host user
could not know which process is in trouble just by guest pid:
the users of container guest only knew the pid inside containers.
This will bring obstacle for trouble shooting.

int getnspid(pid_t pid, int fd1, int fd2, int pidtype);

pid: the pid number need to be translated.

fd: a file descriptor referring to one of
    the namespace entries in a /proc/[pid]/ns/pid.
    fd1 for destination ns(ns1), where the pid came from.
    fd2 for reference ns(ns2), while fd2 = -2 means for current ns.

pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.

return value:
    >0: translated pid in ns1(fd1) seen from ns2(fd2).
    <0: on failure.

Signed-off-by: Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 arch/x86/syscalls/syscall_32.tbl |  1 +
 arch/x86/syscalls/syscall_64.tbl |  1 +
 include/linux/syscalls.h         |  1 +
 kernel/nsproxy.c                 | 60 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)

diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index d6b8679..9de0b32 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -360,3 +360,4 @@
 351	i386	sched_setattr		sys_sched_setattr
 352	i386	sched_getattr		sys_sched_getattr
 353	i386	renameat2		sys_renameat2
+354	i386	getnspid		sys_getnspid
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index ec255a1..1630a8a 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -323,6 +323,7 @@
 314	common	sched_setattr		sys_sched_setattr
 315	common	sched_getattr		sys_sched_getattr
 316	common	renameat2		sys_renameat2
+317	common	getnspid		sys_getnspid
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index b0881a0..271c7b1 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -866,4 +866,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,
 asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
 			 unsigned long idx1, unsigned long idx2);
 asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
+asmlinkage long sys_getpidns(pid_t pid, int fd1, int fd2, int pidtype);
 #endif
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 8e78110..3eda90a 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -261,6 +261,66 @@ out:
 	return err;
 }
 
+SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
+{
+	struct file *file1 = NULL, *file2 = NULL;
+	struct task_struct *task;
+	struct pid_namespace *ns1, *ns2;
+	struct proc_ns *ei;
+	int ret = -1;
+
+	if (pidtype >= PIDTYPE_MAX)
+		return -EINVAL;
+
+	file1 = proc_ns_fget(fd1);
+	if (IS_ERR(file1))
+		return PTR_ERR(file1);
+	ei = get_proc_ns(file_inode(file1));
+	ns1 = (struct pid_namespace *)ei->ns;
+
+	/* fd == -2 for current pid ns */
+	if (fd2 == -2) {
+		ns2 = task_active_pid_ns(current);
+	} else {
+		file2 = proc_ns_fget(fd2);
+		if (IS_ERR(file2)) {
+			fput(file1);
+			return PTR_ERR(file2);
+		}
+		ei = get_proc_ns(file_inode(file2));
+		ns2 = (struct pid_namespace *)ei->ns;
+	}
+
+	rcu_read_lock();
+	task = find_task_by_pid_ns(pid, ns1);
+	rcu_read_unlock();
+	if (!task) {
+		ret = -ESRCH;
+		goto out;
+	}
+
+	switch (pidtype) {
+	case PIDTYPE_PID:
+		ret = task_pid_nr_ns(task, ns2);
+		break;
+	case PIDTYPE_PGID:
+		ret = task_pgrp_nr_ns(task, ns2);
+		break;
+	case PIDTYPE_SID:
+		ret = task_session_nr_ns(task, ns2);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	ret = (ret == 0) ? -ESRCH : ret;
+
+out:
+	fput(file1);
+	if (file2)
+		fput(file2);
+	return ret;
+}
+
 int __init nsproxy_cache_init(void)
 {
 	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
-- 
1.9.0

RE: [PATCH] ns: introduce getnspid syscall

[chenhanxiao-BthXqXjhjHXQFUHtdCDX3A]

> -----Original Message-----
> From: mtk.linux.lists@gmail.com [mailto:mtk.linux.lists@gmail.com] On Behalf Of
> Michael Kerrisk
> Sent: Wednesday, June 18, 2014 2:27 AM
> To: Chen, Hanxiao/陈 晗霄
> Cc: containers; Linux Kernel; Richard Weinberger; Serge Hallyn; Oleg Nesterov;
> David Howells; Eric W. Biederman; Andrew Morton; Al Viro; Linux API; Michael
> Kerrisk-manpages
> Subject: Re: [PATCH] ns: introduce getnspid syscall
> 
> Hello Chen Hanxiao
> 
> On Tue, Jun 17, 2014 at 12:21 PM, Chen Hanxiao
> <chenhanxiao@cn.fujitsu.com> wrote:
> > We need a direct method of getting the pid inside containers.
> > If some issues occurred inside container guest, host user
> > could not know which process is in trouble just by guest pid:
> > the users of container guest only knew the pid inside containers.
> > This will bring obstacle for trouble shooting.
> >
> > int getnspid(pid_t pid, int fd1, int fd2, int pidtype);
> 
> Please CC linux-api@vger.kernel.org on all patches that change the API
> that the kernel presents to user space. See
> https://www.kernel.org/doc/man-pages/linux-api-ml.html
> 
> Thanks,
> 
> Michael
> 
> 
Thanks for reminding.

- Chen
_______________________________________________
Containers mailing list
Containers@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/containers

Re: [PATCH] ns: introduce getnspid syscall

[Pavel Emelyanov]

On 06/17/2014 02:21 PM, Chen Hanxiao wrote:
> We need a direct method of getting the pid inside containers.
> If some issues occurred inside container guest, host user
> could not know which process is in trouble just by guest pid:
> the users of container guest only knew the pid inside containers.
> This will bring obstacle for trouble shooting.
> 
> int getnspid(pid_t pid, int fd1, int fd2, int pidtype);
> 
> pid: the pid number need to be translated.
> 
> fd: a file descriptor referring to one of
>     the namespace entries in a /proc/[pid]/ns/pid.
>     fd1 for destination ns(ns1), where the pid came from.
>     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
> 
> pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
> 
> return value:
>     >0: translated pid in ns1(fd1) seen from ns2(fd2).
>     <0: on failure.
> 
> Signed-off-by: Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/syscalls/syscall_32.tbl |  1 +
>  arch/x86/syscalls/syscall_64.tbl |  1 +
>  include/linux/syscalls.h         |  1 +
>  kernel/nsproxy.c                 | 60 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+)
> 
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index d6b8679..9de0b32 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -360,3 +360,4 @@
>  351	i386	sched_setattr		sys_sched_setattr
>  352	i386	sched_getattr		sys_sched_getattr
>  353	i386	renameat2		sys_renameat2
> +354	i386	getnspid		sys_getnspid
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index ec255a1..1630a8a 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -323,6 +323,7 @@
>  314	common	sched_setattr		sys_sched_setattr
>  315	common	sched_getattr		sys_sched_getattr
>  316	common	renameat2		sys_renameat2
> +317	common	getnspid		sys_getnspid
>  
>  #
>  # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index b0881a0..271c7b1 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -866,4 +866,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,
>  asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
>  			 unsigned long idx1, unsigned long idx2);
>  asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
> +asmlinkage long sys_getpidns(pid_t pid, int fd1, int fd2, int pidtype);
>  #endif
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 8e78110..3eda90a 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -261,6 +261,66 @@ out:
>  	return err;
>  }
>  
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +	struct file *file1 = NULL, *file2 = NULL;
> +	struct task_struct *task;
> +	struct pid_namespace *ns1, *ns2;
> +	struct proc_ns *ei;
> +	int ret = -1;
> +
> +	if (pidtype >= PIDTYPE_MAX)
> +		return -EINVAL;
> +
> +	file1 = proc_ns_fget(fd1);
> +	if (IS_ERR(file1))
> +		return PTR_ERR(file1);
> +	ei = get_proc_ns(file_inode(file1));
> +	ns1 = (struct pid_namespace *)ei->ns;
> +
> +	/* fd == -2 for current pid ns */
> +	if (fd2 == -2) {
> +		ns2 = task_active_pid_ns(current);
> +	} else {
> +		file2 = proc_ns_fget(fd2);
> +		if (IS_ERR(file2)) {
> +			fput(file1);
> +			return PTR_ERR(file2);
> +		}
> +		ei = get_proc_ns(file_inode(file2));
> +		ns2 = (struct pid_namespace *)ei->ns;
> +	}
> +
> +	rcu_read_lock();
> +	task = find_task_by_pid_ns(pid, ns1);
> +	rcu_read_unlock();
> +	if (!task) {
> +		ret = -ESRCH;
> +		goto out;
> +	}
> +
> +	switch (pidtype) {

There's no need in switch, the __task_pid_nr_ns() accepts
the type argument.

> +	case PIDTYPE_PID:
> +		ret = task_pid_nr_ns(task, ns2);

But this is not correct. If task doesn't live in ns2, but ns2
just has the ns->level small enough, then the wrong pid value
would be reported.

> +		break;
> +	case PIDTYPE_PGID:
> +		ret = task_pgrp_nr_ns(task, ns2);
> +		break;
> +	case PIDTYPE_SID:
> +		ret = task_session_nr_ns(task, ns2);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +	ret = (ret == 0) ? -ESRCH : ret;
> +
> +out:
> +	fput(file1);
> +	if (file2)
> +		fput(file2);
> +	return ret;
> +}
> +
>  int __init nsproxy_cache_init(void)
>  {
>  	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
> 

RE: [PATCH] ns: introduce getnspid syscall

[chenhanxiao-BthXqXjhjHXQFUHtdCDX3A]

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> -----Original Message-----
> From: Pavel Emelyanov [mailto:xemul@parallels.com]
> Sent: Tuesday, June 17, 2014 8:13 PM
> To: Chen, Hanxiao/³Â êÏÏö
> Cc: containers@lists.linux-foundation.org; linux-kernel@vger.kernel.org;
> Andrew Morton; Eric W. Biederman; Serge Hallyn; Daniel P. Berrange; Oleg Nesterov;
> Al Viro; David Howells; Richard Weinberger; Vasiliy Kulikov; Gotou, Yasunori/
> Îåu ¿µÎÄ
> Subject: Re: [PATCH] ns: introduce getnspid syscall
> 
> On 06/17/2014 02:21 PM, Chen Hanxiao wrote:
> > We need a direct method of getting the pid inside containers.
> > If some issues occurred inside container guest, host user
> > could not know which process is in trouble just by guest pid:
> > the users of container guest only knew the pid inside containers.
> > This will bring obstacle for trouble shooting.
> >
> > int getnspid(pid_t pid, int fd1, int fd2, int pidtype);
> >
> > pid: the pid number need to be translated.
> >
> > fd: a file descriptor referring to one of
> >     the namespace entries in a /proc/[pid]/ns/pid.
> >     fd1 for destination ns(ns1), where the pid came from.
> >     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
> >
> > pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
> >
> > return value:
> >     >0: translated pid in ns1(fd1) seen from ns2(fd2).
> >     <0: on failure.
> >
> > +	}
> > +
> > +	switch (pidtype) {
> 
> There's no need in switch, the __task_pid_nr_ns() accepts
> the type argument.
> 

Yes, I think we still have that kind of functions, so I used them...

> > +	case PIDTYPE_PID:
> > +		ret = task_pid_nr_ns(task, ns2);
> 
> But this is not correct. If task doesn't live in ns2, but ns2
> just has the ns->level small enough, then the wrong pid value
> would be reported.
> 

Right, we should check whether the task belonged to that namespace firstly.

Thanks,
- Chen

> > +		break;
> > +	case PIDTYPE_PGID:
> > +		ret = task_pgrp_nr_ns(task, ns2);
> > +		break;
> > +	case PIDTYPE_SID:
> > +		ret = task_session_nr_ns(task, ns2);
> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +	}
> > +	ret = (ret == 0) ? -ESRCH : ret;
> > +
> > +out:
> > +	fput(file1);
> > +	if (file2)
> > +		fput(file2);
> > +	return ret;
> > +}
> > +
> >  int __init nsproxy_cache_init(void)
> >  {
> >  	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
> >
> 


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_______________________________________________
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Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
https://lists.linuxfoundation.org/mailman/listinfo/containers

Re: [PATCH] ns: introduce getnspid syscall

[Oleg Nesterov]

On 06/17, Pavel Emelyanov wrote:
>
> On 06/17/2014 02:21 PM, Chen Hanxiao wrote:
> > +	case PIDTYPE_PID:
> > +		ret = task_pid_nr_ns(task, ns2);
>
> But this is not correct. If task doesn't live in ns2, but ns2
> just has the ns->level small enough, then the wrong pid value
> would be reported.

Confused... pid_nr_ns() checks upid->ns == ns and returns zero
otherwise?

Oleg.

Re: [PATCH] ns: introduce getnspid syscall

[Pavel Emelyanov]

On 06/18/2014 10:02 PM, Oleg Nesterov wrote:
> On 06/17, Pavel Emelyanov wrote:
>>
>> On 06/17/2014 02:21 PM, Chen Hanxiao wrote:
>>> +	case PIDTYPE_PID:
>>> +		ret = task_pid_nr_ns(task, ns2);
>>
>> But this is not correct. If task doesn't live in ns2, but ns2
>> just has the ns->level small enough, then the wrong pid value
>> would be reported.
> 
> Confused... pid_nr_ns() checks upid->ns == ns and returns zero
> otherwise?

Yes, you're right. I've missed that line of code :(

> Oleg.
> 
> .
> 

Re: [PATCH] ns: introduce getnspid syscall

[Michael Kerrisk]

Hello Chen Hanxiao

On Tue, Jun 17, 2014 at 12:21 PM, Chen Hanxiao
<chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> wrote:
> We need a direct method of getting the pid inside containers.
> If some issues occurred inside container guest, host user
> could not know which process is in trouble just by guest pid:
> the users of container guest only knew the pid inside containers.
> This will bring obstacle for trouble shooting.
>
> int getnspid(pid_t pid, int fd1, int fd2, int pidtype);

Please CC linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org on all patches that change the API
that the kernel presents to user space. See
https://www.kernel.org/doc/man-pages/linux-api-ml.html

Thanks,

Michael


> pid: the pid number need to be translated.
>
> fd: a file descriptor referring to one of
>     the namespace entries in a /proc/[pid]/ns/pid.
>     fd1 for destination ns(ns1), where the pid came from.
>     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
>
> pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
>
> return value:
>     >0: translated pid in ns1(fd1) seen from ns2(fd2).
>     <0: on failure.
>
> Signed-off-by: Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/syscalls/syscall_32.tbl |  1 +
>  arch/x86/syscalls/syscall_64.tbl |  1 +
>  include/linux/syscalls.h         |  1 +
>  kernel/nsproxy.c                 | 60 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+)
>
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index d6b8679..9de0b32 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -360,3 +360,4 @@
>  351    i386    sched_setattr           sys_sched_setattr
>  352    i386    sched_getattr           sys_sched_getattr
>  353    i386    renameat2               sys_renameat2
> +354    i386    getnspid                sys_getnspid
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index ec255a1..1630a8a 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -323,6 +323,7 @@
>  314    common  sched_setattr           sys_sched_setattr
>  315    common  sched_getattr           sys_sched_getattr
>  316    common  renameat2               sys_renameat2
> +317    common  getnspid                sys_getnspid
>
>  #
>  # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index b0881a0..271c7b1 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -866,4 +866,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,
>  asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
>                          unsigned long idx1, unsigned long idx2);
>  asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
> +asmlinkage long sys_getpidns(pid_t pid, int fd1, int fd2, int pidtype);
>  #endif
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 8e78110..3eda90a 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -261,6 +261,66 @@ out:
>         return err;
>  }
>
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +       struct file *file1 = NULL, *file2 = NULL;
> +       struct task_struct *task;
> +       struct pid_namespace *ns1, *ns2;
> +       struct proc_ns *ei;
> +       int ret = -1;
> +
> +       if (pidtype >= PIDTYPE_MAX)
> +               return -EINVAL;
> +
> +       file1 = proc_ns_fget(fd1);
> +       if (IS_ERR(file1))
> +               return PTR_ERR(file1);
> +       ei = get_proc_ns(file_inode(file1));
> +       ns1 = (struct pid_namespace *)ei->ns;
> +
> +       /* fd == -2 for current pid ns */
> +       if (fd2 == -2) {
> +               ns2 = task_active_pid_ns(current);
> +       } else {
> +               file2 = proc_ns_fget(fd2);
> +               if (IS_ERR(file2)) {
> +                       fput(file1);
> +                       return PTR_ERR(file2);
> +               }
> +               ei = get_proc_ns(file_inode(file2));
> +               ns2 = (struct pid_namespace *)ei->ns;
> +       }
> +
> +       rcu_read_lock();
> +       task = find_task_by_pid_ns(pid, ns1);
> +       rcu_read_unlock();
> +       if (!task) {
> +               ret = -ESRCH;
> +               goto out;
> +       }
> +
> +       switch (pidtype) {
> +       case PIDTYPE_PID:
> +               ret = task_pid_nr_ns(task, ns2);
> +               break;
> +       case PIDTYPE_PGID:
> +               ret = task_pgrp_nr_ns(task, ns2);
> +               break;
> +       case PIDTYPE_SID:
> +               ret = task_session_nr_ns(task, ns2);
> +               break;
> +       default:
> +               ret = -EINVAL;
> +       }
> +       ret = (ret == 0) ? -ESRCH : ret;
> +
> +out:
> +       fput(file1);
> +       if (file2)
> +               fput(file2);
> +       return ret;
> +}
> +
>  int __init nsproxy_cache_init(void)
>  {
>         nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
> --
> 1.9.0
>
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linuxfoundation.org/mailman/listinfo/containers



-- 
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/

Re: [PATCH] ns: introduce getnspid syscall

[Eric W. Biederman]

Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> writes:

> We need a direct method of getting the pid inside containers.
> If some issues occurred inside container guest, host user
> could not know which process is in trouble just by guest pid:
> the users of container guest only knew the pid inside containers.
> This will bring obstacle for trouble shooting.

There is also some ongoing work to export this information via a proc
file which may be more appropriate.  Certainly for debugging something
easily human discoverable sounds more appropriate.

> int getnspid(pid_t pid, int fd1, int fd2, int pidtype);

The pidtype is nonsense.  The translation of a pid does not depend upon
type.  And using that kind of nonsense will just lead you into confusion.

> pid: the pid number need to be translated.
>
> fd: a file descriptor referring to one of
>     the namespace entries in a /proc/[pid]/ns/pid.
>     fd1 for destination ns(ns1), where the pid came from.
>     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
>
> pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
>
> return value:
>     >0: translated pid in ns1(fd1) seen from ns2(fd2).
>     <0: on failure.

Elsewhere we use 0 on pid translation failure.  Why be different here?

Eric


> Signed-off-by: Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/syscalls/syscall_32.tbl |  1 +
>  arch/x86/syscalls/syscall_64.tbl |  1 +
>  include/linux/syscalls.h         |  1 +
>  kernel/nsproxy.c                 | 60 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+)
>
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index d6b8679..9de0b32 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -360,3 +360,4 @@
>  351	i386	sched_setattr		sys_sched_setattr
>  352	i386	sched_getattr		sys_sched_getattr
>  353	i386	renameat2		sys_renameat2
> +354	i386	getnspid		sys_getnspid
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index ec255a1..1630a8a 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -323,6 +323,7 @@
>  314	common	sched_setattr		sys_sched_setattr
>  315	common	sched_getattr		sys_sched_getattr
>  316	common	renameat2		sys_renameat2
> +317	common	getnspid		sys_getnspid
>  
>  #
>  # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index b0881a0..271c7b1 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -866,4 +866,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,
>  asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
>  			 unsigned long idx1, unsigned long idx2);
>  asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
> +asmlinkage long sys_getpidns(pid_t pid, int fd1, int fd2, int pidtype);
>  #endif
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 8e78110..3eda90a 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -261,6 +261,66 @@ out:
>  	return err;
>  }
>  
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +	struct file *file1 = NULL, *file2 = NULL;
> +	struct task_struct *task;
> +	struct pid_namespace *ns1, *ns2;
> +	struct proc_ns *ei;
> +	int ret = -1;
> +
> +	if (pidtype >= PIDTYPE_MAX)
> +		return -EINVAL;
> +
> +	file1 = proc_ns_fget(fd1);
> +	if (IS_ERR(file1))
> +		return PTR_ERR(file1);
> +	ei = get_proc_ns(file_inode(file1));
> +	ns1 = (struct pid_namespace *)ei->ns;
> +
> +	/* fd == -2 for current pid ns */
> +	if (fd2 == -2) {
> +		ns2 = task_active_pid_ns(current);
> +	} else {
> +		file2 = proc_ns_fget(fd2);
> +		if (IS_ERR(file2)) {
> +			fput(file1);
> +			return PTR_ERR(file2);
> +		}
> +		ei = get_proc_ns(file_inode(file2));
> +		ns2 = (struct pid_namespace *)ei->ns;
> +	}
> +
> +	rcu_read_lock();
> +	task = find_task_by_pid_ns(pid, ns1);
> +	rcu_read_unlock();
> +	if (!task) {
> +		ret = -ESRCH;
> +		goto out;
> +	}
> +
> +	switch (pidtype) {
> +	case PIDTYPE_PID:
> +		ret = task_pid_nr_ns(task, ns2);
> +		break;
> +	case PIDTYPE_PGID:
> +		ret = task_pgrp_nr_ns(task, ns2);
> +		break;
> +	case PIDTYPE_SID:
> +		ret = task_session_nr_ns(task, ns2);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +	ret = (ret == 0) ? -ESRCH : ret;
> +
> +out:
> +	fput(file1);
> +	if (file2)
> +		fput(file2);
> +	return ret;
> +}
> +
>  int __init nsproxy_cache_init(void)
>  {
>  	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);

Re: [PATCH] ns: introduce getnspid syscall

[Eric W. Biederman]

Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org> writes:

> We need a direct method of getting the pid inside containers.
> If some issues occurred inside container guest, host user
> could not know which process is in trouble just by guest pid:
> the users of container guest only knew the pid inside containers.
> This will bring obstacle for trouble shooting.

There is also some ongoing work to export this information via a proc
file which seems more appropriate for solving your problem.  Certainly
for debugging something easily human discoverable is needed.

> int getnspid(pid_t pid, int fd1, int fd2, int pidtype);

The pidtype is nonsense.  The translation of a pid does not depend upon
type.  Using that kind of nonsense will lead you and others into confusion.

> pid: the pid number need to be translated.
>
> fd: a file descriptor referring to one of
>     the namespace entries in a /proc/[pid]/ns/pid.
>     fd1 for destination ns(ns1), where the pid came from.
>     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
>
> pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
>
> return value:
>     >0: translated pid in ns1(fd1) seen from ns2(fd2).
>     <0: on failure.

Elsewhere we use 0 on pid translation failure.  Why be different here?

Eric


> Signed-off-by: Chen Hanxiao <chenhanxiao-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  arch/x86/syscalls/syscall_32.tbl |  1 +
>  arch/x86/syscalls/syscall_64.tbl |  1 +
>  include/linux/syscalls.h         |  1 +
>  kernel/nsproxy.c                 | 60 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 63 insertions(+)
>
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index d6b8679..9de0b32 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -360,3 +360,4 @@
>  351	i386	sched_setattr		sys_sched_setattr
>  352	i386	sched_getattr		sys_sched_getattr
>  353	i386	renameat2		sys_renameat2
> +354	i386	getnspid		sys_getnspid
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index ec255a1..1630a8a 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -323,6 +323,7 @@
>  314	common	sched_setattr		sys_sched_setattr
>  315	common	sched_getattr		sys_sched_getattr
>  316	common	renameat2		sys_renameat2
> +317	common	getnspid		sys_getnspid
>  
>  #
>  # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index b0881a0..271c7b1 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -866,4 +866,5 @@ asmlinkage long sys_process_vm_writev(pid_t pid,
>  asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
>  			 unsigned long idx1, unsigned long idx2);
>  asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
> +asmlinkage long sys_getpidns(pid_t pid, int fd1, int fd2, int pidtype);
>  #endif
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 8e78110..3eda90a 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -261,6 +261,66 @@ out:
>  	return err;
>  }
>  
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +	struct file *file1 = NULL, *file2 = NULL;
> +	struct task_struct *task;
> +	struct pid_namespace *ns1, *ns2;
> +	struct proc_ns *ei;
> +	int ret = -1;
> +
> +	if (pidtype >= PIDTYPE_MAX)
> +		return -EINVAL;
> +
> +	file1 = proc_ns_fget(fd1);
> +	if (IS_ERR(file1))
> +		return PTR_ERR(file1);
> +	ei = get_proc_ns(file_inode(file1));
> +	ns1 = (struct pid_namespace *)ei->ns;
> +
> +	/* fd == -2 for current pid ns */
> +	if (fd2 == -2) {
> +		ns2 = task_active_pid_ns(current);
> +	} else {
> +		file2 = proc_ns_fget(fd2);
> +		if (IS_ERR(file2)) {
> +			fput(file1);
> +			return PTR_ERR(file2);
> +		}
> +		ei = get_proc_ns(file_inode(file2));
> +		ns2 = (struct pid_namespace *)ei->ns;
> +	}
> +
> +	rcu_read_lock();
> +	task = find_task_by_pid_ns(pid, ns1);

The functions you want to be using here are:
find_pid_ns and pid_nr_ns.

> +	rcu_read_unlock();
> +	if (!task) {
> +		ret = -ESRCH;
> +		goto out;
> +	}
> +
> +	switch (pidtype) {
> +	case PIDTYPE_PID:
> +		ret = task_pid_nr_ns(task, ns2);
> +		break;
> +	case PIDTYPE_PGID:
> +		ret = task_pgrp_nr_ns(task, ns2);
> +		break;
> +	case PIDTYPE_SID:
> +		ret = task_session_nr_ns(task, ns2);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +	ret = (ret == 0) ? -ESRCH : ret;
> +
> +out:
> +	fput(file1);
> +	if (file2)
> +		fput(file2);
> +	return ret;
> +}
> +
>  int __init nsproxy_cache_init(void)
>  {
>  	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);

RE: [PATCH] ns: introduce getnspid syscall

[chenhanxiao-BthXqXjhjHXQFUHtdCDX3A]

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Hi,

> -----Original Message-----
> From: Eric W. Biederman [mailto:ebiederm@xmission.com]
> Sent: Wednesday, June 18, 2014 9:31 AM
> To: Chen, Hanxiao/³Â êÏÏö
> Cc: containers@lists.linux-foundation.org; linux-kernel@vger.kernel.org;
> Andrew Morton; Serge Hallyn; Daniel P. Berrange; Oleg Nesterov; Al Viro; David
> Howells; Richard Weinberger; Pavel Emelyanov; Vasiliy Kulikov; Gotou, Yasunori/
> Îåu ¿µÎÄ; Linux API; Michael Kerrisk-manpages
> Subject: Re: [PATCH] ns: introduce getnspid syscall
> 
> Chen Hanxiao <chenhanxiao@cn.fujitsu.com> writes:
> 
> > We need a direct method of getting the pid inside containers.
> > If some issues occurred inside container guest, host user
> > could not know which process is in trouble just by guest pid:
> > the users of container guest only knew the pid inside containers.
> > This will bring obstacle for trouble shooting.
> 
> There is also some ongoing work to export this information via a proc
> file which seems more appropriate for solving your problem.  Certainly
> for debugging something easily human discoverable is needed.
> 

Do you mean this patch:
/proc/pid/status: show all sets of pid according to ns
https://lkml.org/lkml/2014/5/26/145

But no new comments on this patch,
Pavel suggested that a syscall should be a good choice.
Do we should continue this kind of work?

> > int getnspid(pid_t pid, int fd1, int fd2, int pidtype);
> 
> The pidtype is nonsense.  The translation of a pid does not depend upon
> type.  Using that kind of nonsense will lead you and others into confusion.
> 

I see.

> > pid: the pid number need to be translated.
> >
> > fd: a file descriptor referring to one of
> >     the namespace entries in a /proc/[pid]/ns/pid.
> >     fd1 for destination ns(ns1), where the pid came from.
> >     fd2 for reference ns(ns2), while fd2 = -2 means for current ns.
> >
> > pidtype: 0 PIDTYPE_PID; 1 PIDTYPE_PGID; 2 PIDTYPE_SID.
> >
> > return value:
> >     >0: translated pid in ns1(fd1) seen from ns2(fd2).
> >     <0: on failure.
> 
> Elsewhere we use 0 on pid translation failure.  Why be different here?
> 

It should be <=0. And <0 means some other failures.

> Eric
> 
> 
> > Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
> > +
> > +	rcu_read_lock();
> > +	task = find_task_by_pid_ns(pid, ns1);
> 
> The functions you want to be using here are:
> find_pid_ns and pid_nr_ns.
> 

Thanks for your hint.

- Chen



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Re: [PATCH] ns: introduce getnspid syscall

[Oleg Nesterov]

On 06/17, Chen Hanxiao wrote:
>
> +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> +{
> +	struct file *file1 = NULL, *file2 = NULL;
> +	struct task_struct *task;
> +	struct pid_namespace *ns1, *ns2;
> +	struct proc_ns *ei;
> +	int ret = -1;
> +
> +	if (pidtype >= PIDTYPE_MAX)
> +		return -EINVAL;
> +
> +	file1 = proc_ns_fget(fd1);
> +	if (IS_ERR(file1))
> +		return PTR_ERR(file1);
> +	ei = get_proc_ns(file_inode(file1));
> +	ns1 = (struct pid_namespace *)ei->ns;

and I am not sure this part is correct... shouldn't we also verify that
ns_ops == pidns_operations ?

Perhaps it makes sense to generalize get_net_ns_by_fd() into
"void *get_ns_by_fd(fd, type)"... this probably needs another "check-and-get"
method in proc_ns_operations(). I dunno.

Oleg.

RE: [PATCH] ns: introduce getnspid syscall

[chenhanxiao-BthXqXjhjHXQFUHtdCDX3A]

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> -----Original Message-----
> From: Oleg Nesterov [mailto:oleg@redhat.com]
> Sent: Thursday, June 19, 2014 1:58 AM
> To: Chen, Hanxiao/³Â êÏÏö
> Cc: containers@lists.linux-foundation.org; linux-kernel@vger.kernel.org;
> Andrew Morton; Eric W. Biederman; Serge Hallyn; Daniel P. Berrange; Al Viro; David
> Howells; Richard Weinberger; Pavel Emelyanov; Vasiliy Kulikov; Gotou, Yasunori/
> Îåu ¿µÎÄ
> Subject: Re: [PATCH] ns: introduce getnspid syscall
> 
> On 06/17, Chen Hanxiao wrote:
> >
> > +SYSCALL_DEFINE4(getnspid, pid_t, pid, int, fd1, int, fd2, int, pidtype)
> > +{
> > +	struct file *file1 = NULL, *file2 = NULL;
> > +	struct task_struct *task;
> > +	struct pid_namespace *ns1, *ns2;
> > +	struct proc_ns *ei;
> > +	int ret = -1;
> > +
> > +	if (pidtype >= PIDTYPE_MAX)
> > +		return -EINVAL;
> > +
> > +	file1 = proc_ns_fget(fd1);
> > +	if (IS_ERR(file1))
> > +		return PTR_ERR(file1);
> > +	ei = get_proc_ns(file_inode(file1));
> > +	ns1 = (struct pid_namespace *)ei->ns;
> 
> and I am not sure this part is correct... shouldn't we also verify that
> ns_ops == pidns_operations ?
> 
You're right. We should check this part.

Thanks,
- Chen

> Perhaps it makes sense to generalize get_net_ns_by_fd() into
> "void *get_ns_by_fd(fd, type)"... this probably needs another "check-and-get"
> method in proc_ns_operations(). I dunno.
> 
> Oleg.


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